The association had originally proposed a more ambitious trail-improvement project in the 330-acre North Street park, but wetlands and other issues have derailed that for now.

"There have been rumors flying around that mountain bikers are destroying other parks that they are allowed to use," said Bill McCarthy, the city recreation director. "But our research shows that it was another group, not this one, involved in that."

McCarthy said that one of the concerns raised is that the mountain bikers could be doing work as volunteers that unionized municipal employees are entitled to do.

The rec commission cleared the way for the mountain biking association last spring, but that tentative approval carried conditions, McCarthy said.

"We gave them our blessing, but they still had to jump through some hoops," the city official said. "We want to know how they intend to improve the existing trails and to what extent that would give them the right to use them."

Woyciesjes said the purpose of the NEMBA is to improve existing trails, not to build new ones, and that the trails would be open to everyone.

Portions of the nearly 11 miles of hiking and biking trails through Eisenhower Park have erosion problems or are otherwise in poor condition, he said.